Here is a JUnit test case to test the OM's conformance against W3C test suite (available at the url http://dev.w3.org/cvsweb/2001/XML-Test-Suite/). Make sure to have in the directory of test case a folder named "XMLSuite" which contains in it all the unzipped files of the W3C XML test suite.

Here is the listing of the test case code. 

/*
 * Created on Apr 8, 2005
 *
 * TODO To change the template for this generated file go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
package junittesting;

import java.io.File;
import org.custommonkey.xmlunit.XMLTestCase;
import org.custommonkey.xmlunit.Diff;
import org.apache.axis.om.OMElement;
import org.apache.axis.om.impl.llom.factory.OMXMLBuilderFactory;
import org.apache.axis.om.impl.llom.builder.StAXOMBuilder;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamWriter;
import javax.xml.stream.XMLStreamException;
import org.apache.axis.om.OMFactory;
import java.io.FileOutputStream;
import java.io.FileReader;


/**
 * @author sunja07
 *
 * TODO To change the template for this generated type comment go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
public class XMLConformanceTest extends XMLTestCase {

        private static int successCount=0;
        private static int parsedCount=0;
        private static int fileCount=0;

        /**
         * @param name
         */
        public XMLConformanceTest(String name) {
                super(name);
        }

        public void setUp() {
        }

        public void testXMLConformance() throws Exception{
                File testSuiteDirectory = new File("XMLSuite");
                ProcessDir(testSuiteDirectory);
                System.out.println("Total file count is " + fileCount);
                System.out.println("Parsed count is " + parsedCount +". This is just partial success");
                System.out.println("Complete success count is " + successCount);
        }

        public void ProcessDir(File dir) throws Exception
        {
                if (dir.isDirectory()) {
                        //System.out.println("Processing Directory: "+dir.getAbsolutePath() );
                        String[] children = dir.list();
                        for (int i=0; i<children.length; i++) {
                   File child = (new File(dir, children[i]));
                        ProcessDir(child);
                   }

            } else { //meaning you got a file
                //check if it's xml file
                String absPath = dir.getAbsolutePath();
                if(absPath.endsWith(".xml")) {
                        //process it
                        testSingleFileConformance(absPath);
                } else {
                        //ignore non .xml files
                }
        }
        }

        public void testSingleFileConformance(String absolutePath) throws Exception{
                OMElement rootElement;
             fileCount++;
                //get a stax om builder out of the file. LOAD step
                try {
                        StAXOMBuilder staxOMBuilder=OMXMLBuilderFactory.createStAXOMBuilder( OMFactory.newInstance(), XMLInputFactory.newInstance().createXMLStreamReader(new FileReader(absolutePath)));

                        rootElement = staxOMBuilder.getDocumentElement();
                } catch (Exception e) {
                        System.err.println("Exception trying to get hold of rootElement: " + e.getMessage());
                        System.err.println("in file: "+ absolutePath +"\n");
                        return;
                }

                //we will write output into the file named TempOutputFile.txt in current directory. SAVE step

                String tempFile = "TempOutputFile.txt";
                XMLStreamWriter writer;
                try {
                   writer = XMLOutputFactory.newInstance().createXMLStreamWriter(new FileOutputStream(tempFile));
                rootElement.serialize(writer, true);
                }catch(XMLStreamException e) {
                        System.err.println("Error in creating XMLStreamWriter to write parsed xml into");
                        return;
                } catch (Exception e) {
                        System.err.println("Exception while serializing: " + e.getMessage());
                        System.err.println("in file: "+ absolutePath +"\n");
                        return;
                }

                writer.flush();

                writer.close();

                parsedCount++;


        //Comparing the equality of the TempOutputFile.txt and the input xml is due. COMPARE step

        Diff diff;

        try {
                diff = compareXML(new FileReader(absolutePath), new FileReader("TempOutputFile.txt"));
        } catch (Exception e) {
                System.out.println("Error comparing original and generated files for: "+absolutePath);
                return;
        }
        try {
                assertXMLEqual(diff,true);

                successCount++;
        } catch (Error e) {
                System.out.println("XMLEquality failed for file: "+absolutePath);

                return;
        }

        }

        public void tearDown() {
        }

}